It's one of the most common, and most poorly understood, sleep disorders. Sexsomniacs have sex with bedmates in their sleep, or sometimes while sleep walking. Now a new study sheds light on the phenomenon.

Presented today at the annual meeting of the Associated Professional Sleep Societies, this new study of sexsomnia revealed that 7.6 percent of people who sought treatment for sleep disorders also have somnolent sex lives. Apparently rates of sexsomnia are higher in men than women, but the researchers admit that the numbers may be affected by the fact that people are often reluctant to admit to having this problem. Few people admit to sexsomnia, so there is little data about it.

According to the American Academy of Sleep Medicine:

The study involved a retrospective chart review of 832 consecutive patients who were evaluated for a suspected sleep disorder; the sample consisted of 428 men and 404 women. Patients completed a questionnaire about sleep disorders symptoms, behaviors during sleep, sleepiness, fatigue and mood.

Symptoms of insomnia, fatigue and depressed mood were similar between people reporting sexsomnia and other patients at the sleep disorders center. Both groups also had similar rates of smoking and caffeine consumption. However, people who reported sexsomnia were twice as likely as other sleep center patients to admit using illicit drugs (15.9 percent vs. 7.7 percent). . . A literature review in the June 2007 issue of the journal SLEEP concluded that a broad range of sleep-related disorders are associated with abnormal sexual behaviors and experiences.

So let me get this straight. People who use "illicit drugs" have more sex while sleeping. So somehow this biological disorder hinges on cultural and legal norms about drugs. And in addition, sexsomniacs are also prone to "abnormal sexual behaviors and experiences." Which means what, exactly? People who like using those fluffy pink handcuffs from the novelty store are more likely to have sex while sleeping?

This study has so many unexamined assumptions that I'm not going to lose any sleep over it.